A variety of conventional pedicle screws are known to those of ordinary skill in the art. These pedicle screws typically consist of a threaded screw portion including an enlarged head end and a head body. The threaded screw portion engages a pedicle of a vertebra of the spine, and the head body engages the threaded screw portion, optionally by passing the threaded screw portion down and through a hole manufactured into the bottom of the head body until the head end is seated in the bottom portion of the head body. The pedicle screws can be monoaxial or polyaxial, allowing the head body multiple degrees of freedom with respect to the threaded screw portion. Once placed, rods are inserted into the head bodies of adjacent pedicle screws and set screws are placed to simultaneously secure the head bodies to their respective threaded screw portions and to lock the rods in place. A rigid framework is thereby formed, stabilizing and fixing the vertebrae of the spine.
Typically, these pedicle screws are placed in a pre-assembled configuration, with the head body joined to the threaded screw portion. It is desirable, however, that a surgeon have a pedicle screw that may be placed in a substantially disassembled configuration, first placing the threaded screw portion, and then screwing the head body onto the threaded screw portion, at all times maintaining the polyaxial nature of the pedicle screw such that rods may be inserted as necessary before everything is locked together. The present invention provides such a pedicle screw.